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### Re^6: Binary to decimal conversion

by andreas1234567 (Vicar)
 on Dec 11, 2007 at 13:57 UTC ( #656407=note: print w/replies, xml ) Need Help??

in reply to Re^5: Binary to decimal conversion
in thread Binary to decimal conversion

Then tell me why this prints hello and not olleh?
```\$ perl -wle 'print reverse(q{hello})'
hello
--
Andreas

Replies are listed 'Best First'.
Re^7: Binary to decimal conversion
by Fletch (Chancellor) on Dec 11, 2007 at 14:02 UTC

Because print takes a LIST and hence provides a list context to reverse which triggers the list context behavior from the latter (and a 1 element list reversed is indistinguishable from the original 1 element list for obvious reasons). Stick a scalar in there after the print, and/or store the reverse into a scalar temporary variable, and you'll see the behavior you're expecting.

The cake is a lie.
The cake is a lie.
The cake is a lie.

Said code (and then some):
```\$\ = "\n";

print(my @a = reverse('hello'));  # hello (order or scalars reversed)
print(my \$s = reverse('hello'));  # olleh (order of chars reversed)

print(reverse('hello'));          # hello (order or scalars reversed)
print(scalar(reverse('hello')));  # olleh (order of chars reversed)

sub f(@) { return @_; }
sub g(\$) { return @_; }

print(f(reverse('hello'));        # hello (order or scalars reversed)
print(g(reverse('hello')));       # olleh (order of chars reversed)
Re^7: Binary to decimal conversion
by Anonymous Monk on Dec 12, 2007 at 08:34 UTC
Because you did not RTFM :)
```reverse LIST
In list context, returns a list value consisting of the elemen
+ts
of LIST in the opposite order. In scalar context, concatenates
the elements of LIST and returns a string value with all
characters in the opposite order.

print reverse <>;           # line tac, last line first

undef \$/;                   # for efficiency of <>
print scalar reverse <>;    # character tac, last line tsr
+if

Used without arguments in scalar context, reverse() reverses \$
+_.

This operator is also handy for inverting a hash, although the
+re
are some caveats. If a value is duplicated in the original has
+h,
only one of those can be represented as a key in the inverted
hash. Also, this has to unwind one hash and build a whole new
one, which may take some time on a large hash, such as from a
DBM file.

%by_name = reverse %by_address;     # Invert the hash

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